Brute-force 4 digit pin with pass using shell script

I am doing some challenges. This is one them. I am trying to brute-force 4 digit pin with the password to get my desired answer. After connecting to the port It prompts me to enter the password then space then 4 digit pin. I tried to brute-force the pin using the script: #!/bin/bash nc localhost 30002 sleep 2 for i in {0000..9999}; if [[ $(echo 'UoMYTrfrBFHyQXmg6gzctqAwOmw1IohZ $i' if [[ $(echo 'UoMYTrfrBFHyQXmg6gzctqAwOmw1IohZ $i') = ^Wrong* ]]; What am I doing wrong here? UPDATE: ---------------------------------------------------- Okay, so after researching around. I wrote this: for i in {0000..9999} do if [ (echo "UoMYTrfrBFHyQXmg6gzctqAwOmw1IohZ $i" | nc localhost 30002 | grep -o Wrong) == "Wrong" ] then sleep 0.1 continue fi echo "- - - - - - - - - - - - - - - - - - - - - - - - [$i]" done This might even work but as you can see it opens new connections in the loop which makes it really slow and exhaust the system.